1. Technical Field of the Invention
The present invention relates to a tape cassette storage case, particularly to a technique for steadily protecting a tape cassette encased inside from impact of dropping or the like.
2. Description of the Related Art
In a related art hard case used for encasing a tape cassette, impact resistance for protecting the tape cassette encased therein, even when user has dropped the case by mistake, is required. In order to improve the impact resistance, it is necessary to use a tape cassette and a case that are capable of absorbing or sustaining the impact energy.
However, a design limitation exists in the improvement in the strength of the tape cassette structure. Therefore, it is preferable that the related art case can absorb the impact energy on its own without changing the tape structure, thereby protecting the tape cassette.
In this way, for protecting the tape cassette from the impact of dropping or the like, a tape cassette storage case provided with a bumper portion at the periphery is known in the related art (see, for example JP-A 2002-179176).
As described in FIG. 10, this tape cassette storage case 1 is provided with a case body 2 for storing a tape cassette, and a lid portion 3 for covering an opening above the case body 2. The case body 2 is provided with a bottom plate 2a, and side walls 2b are set up along the periphery of the bottom plate 2a. 
Meanwhile, the lid portion 3 is provided with an upper plate 3a that is connected to the bottom plate 2a of the case body 2 by a hinge 4a, a connecting plate 5, and a hinge 4b at one side of the upper plate 3a. The case body 2 and the lid portion 3 can open or close relative to each other, and side walls 3b are provided along the other three sides.
In convex portions 6 on the bottom plate 2a of the case body 2, projection portions 7 are set up to support a tape cassette such that the projections can be inserted into reel hub holes of the tape cassette. In addition, in the inner four corners of the upper plate 3a of the lid portion 3, bosses 8 are provided to hold the tape cassette therebetween. Furthermore, thin-walled portions 10 are formed to project on the outsides of the side walls 2b of the bottom plate 2a of the case body 2 and the side walls 3b of the upper plate 3a, as being operable to bumpers.
When user unintentionally drops the tape cassette storage case 1 and the impact strength is applied against the bottom plate 2a and the upper plate 3a in the direction perpendicular to the plates 2a, 3a, the convex portions 6 formed on the bottom plate 2a become elastically deformed toward the direction of the tape cassette thickness, thereby relieving the impact to be applied to the tape cassette. By this means, the reel and the tape cassette are prevented from being damaged.
Also, when the tape cassette storage case is dropped on its corner or on its side surface, the thin-walled portions 10 function as bumper portions and deform. Thus, the encased tape cassette is relieved from the impact.
However, more specifically, when the tape cassette storage case 1 is subjected to being dropped from its corner, the impact energy concentrates on the corner. Thus, there is a need to thicken the thin-walled portions 10, because if the thin-walled portions 10 are formed too thin, the thin-walled portions 10 are damaged or plastically deformed on its own.
On the contrary, if the thin-walled portions 10 are formed too thick, the rigidity of the case is too high and there is a difficulty in absorbing the impact energy. Therefore, the bumper function becomes low. As a result, the tape cassette storage case can neither absorb the impact energy nor protect the tape cassette encased therein. Although the suitable thickness of the thin-walled portions 10 differs depending on the direction of the drop, when the tape cassette storage case 1 is specifically subjected to the corner drop (i.e., dropped on its corner), since the impact energy concentrates on the corner, deformation of the thin-walled portion 10 on the corner are large in comparison with the deformation that occurs when the tape cassette storage case 1 is subjected to the plane drop (i.e., dropped on the side walls 2b, 3b). Accordingly, there has been no uniform thickness of the thin-walled portions 10 having bumper capability suitable for the both drops.